This will keep a couple of days in the refrigerator and will be safe to drink for longer than that, but the texture changes and the taste fades so it's best when used the same day. For a party, it's lovely to make another batch using a yellow watermelon or a cantaloupe, and a pale green one with honeydew melon.
2. Taste and add sugar if necessary, stirring until dissolved. If the watermelon is not quite at its peak and the flavor needs brightening, add lemon or lime juice to taste. Chill. Stir before serving.
Sandor Katz lives to ferment; it’s his life’s work. The author of The Art of Fermentation shares how to make kombucha at home.